Biology subjects

Pederson, T.

Publications and source records attributed to Pederson, T..

8 recordsLinked to original sources

bioRxiv2026

Bioplastic Production from simulated 100% in situ Mars resources

A sustained human presence on Mars requires local production of bulk materials, particularly polymers. Prior approaches to space biomanufacturing rely on human waste streams, Earth-sourced consumables, or complex chemical infrastructure, limiting their ability to scale. Here we demonstrate production of polyhydroxyalkanoate (PHA) bioplastic from simulated 100% martian resources: regolith-derived soluble nutrients, acetate electrochemically fixed from martian atmosphere, and water. We screened 16 candidate organisms for growth in a chemically defined Mars medium and identified Cupriavidus necator H16 and Pseudomonas putida KT2440 as promising chassis organisms. Adaptive laboratory evolution totaling more than 1012 cumulative cell divisions improved both species' tolerance to high concentrations of acetate and leached regolith. The top C. necator evolved isolate, referred to as sPL.001, produced more than three-fold higher PHA titer under simulated Mars conditions compared to its parent strain. These results establish a path to polymer production on Mars where consumable mass is derived entirely from local resources, decoupling bulk material production from Earth supply chains.

bioengineering↗

bioRxiv2026

OTTR-CLASH: improved biochemical and bioinformatic identification of Argonaute 2-mediated microRNA-target RNA interactions

Various methods have detected miRNA-target interactions via immunoprecipitation of UV-crosslinked Argonaute ribonucleoprotein complexes, followed by intermolecular ligation of bound miRNAs to target strands, forming chimeric RNAs. To date, these methods have relied on conventional viral reverse transcriptases (RTs) to generate cDNAs for sequencing. However, crosslinked RNAs often retain adducts after purification, which can make them poor templates for viral RTs. Here, we adapted OTTR (Ordered Two-Template Relay) techniques to generate cDNAs from Ago2-bound RNAs. OTTR makes use of a modified retroelement-encoded RT, which is strongly processive even on templates with modifications or adducts. We show that this "OTTR-CLASH" method increases the frequency of generating chimeric RNAs compared to previous methods. We also developed an improved bioinformatic pipeline for analysis of these data, and we use this to catalog miRNA-target interactions not previously described in the literature. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=147 HEIGHT=200 SRC="FIGDIR/small/738487v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@16d62f8org.highwire.dtl.DTLVardef@7c8da4org.highwire.dtl.DTLVardef@13727fborg.highwire.dtl.DTLVardef@21f443_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2025

High throughput screen of NPQ in sorghum shows highly polygenic architecture of photoprotection

O_LINatural genetic variation in photosynthesis and photoprotection within crop germplasm represents an untapped resource for crop improvement. Sorghum bicolor (sorghum) is one of the worlds most widely grown crops, yet the genetic basis of photoprotection in sorghum is not well understood. C_LIO_LIThis study examined genetic variation in non-photochemical quenching traits by screening a field-grown panel of 861 genetically diverse natural sorghum accessions across two years. C_LIO_LIBroad-sense heritability ranged between 0.3 to 0.65 across different chlorophyll fluorescence parameters. A combination of genome- and transcriptome-wide (GWAS and TWAS) identification of genetic correlates with the observed trait variation uncovered a complex genetic architecture of many significant small-effect loci. An ensemble approach based on GWAS and TWAS results and the covariance between different fluorescence parameters was used to identify 110 unique candidate genes. C_LIO_LIThe resulting high-confidence candidates reveal novel genetic associations with photoprotection and offer resources for further genetic studies and crop genomic improvement efforts. C_LI

plant biology↗

bioRxiv2023

Nucleolar structure connects with global nuclear organization

The nucleolus is a multi-functional nuclear body. To tease out the roles of nucleolar structure without resorting to multi-action drugs, we knocked down RNA polymerase I subunit RPA194 in HeLa cells by siRNA. Loss of RPA194 resulted in nucleolar structural segregation and effects on both nucleolus-proximal and distal nuclear components. The perinucleolar compartment was disrupted, centromere-nucleolus interactions were significantly reduced, and the intranuclear locations of specific genomic loci were altered. Moreover, Cajal bodies, distal from nucleoli, underwent morphological and compositional changes. To distinguish whether these global reorganizations are the results of nucleolar structural disruption or inhibition of ribosome synthesis, the pre-ribosomal RNA processing factor, UTP4, was also knocked down, which did not lead to nucleolar segregation, nor the intranuclear effects seen with RPA195A knockdown, demonstrating that they do not arise from a cessation of ribosome synthesis. These findings point to a commutative system that links nucleolar structure to the maintenance and spatial organization of certain nuclear bodies and genomic loci.

cell biology↗

bioRxiv2020

Simultaneous Epigenetic Perturbation and Genome Imaging Reveal Distinct Roles of H3K9me3 in Chromatin Architecture and Transcription

Despite the long-observed correlation between H3K9me3, chromatin architecture and transcriptional repression, how H3K9me3 regulates genome higher-order organization and transcriptional activity in living cells remains unclear. Here we develop EpiGo (Epigenetic perturbation induced Genome organization)-KRAB to introduce H3K9me3 at hundreds of loci spanning megabases on human chromosome 19 and simultaneously track genome organization. EpiGo-KRAB is sufficient to induce de novo heterochromatin-like domain formation, which requires SETDB1, a methyltransferase of H3K9me3. Unexpectedly, EpiGo-KRAB induced heterochromatin-like domain does not result in widespread gene repression except a small set of genes with concurrent loss of H3K4me3 and H3K27ac. Ectopic H3K9me3 appears to spread in inactive regions but is largely restricted to transcriptional initiation sites in active regions. Finally, Hi-C analysis showed that EpiGo-KRAB induced to reshape existing compartments. These results reveal the role of H3K9me3 in genome organization could be partially separated from its function in gene repression.

molecular biology↗

bioRxiv2020

CRISPR-based Live Imaging of Epigenetic Modification-Mediated Genome Reorganization

Epigenetic modifications play an essential role in chromatin architecture and dynamics. The role of epigenetic modification in chromatin organization has been studied by Hi-C from population cells, but imaging techniques to study their correlation and regulation in single living cells are lacking. Here we develop a CRISPR-based EpiGo (Epigenetic perturbation induced Genome organization) system to track epigenetic modification-mediated relocation, interaction or reorganization of genomic regions in living cells. EpiGo-KRAB is sufficient to induce the relocation of genomic loci to HP1 condensates and trigger genomic interactions. EpiGo-KRAB also triggers the induction of H3K9me3 at large genomic regions, which decorate on the surface of HP1 condensates possibly driven by phase separation.

molecular biology↗

bioRxiv2019

Direct, sensitive and specific detection of individual single- or double-strand DNA breaks by fluorescence microscopy

We here describe a technique termed STRIDE (SensiTive Recognition of Individual DNA Ends), which enables highly sensitive, specific, direct in situ detection of single- or double-strand DNA breaks (sSTRIDE or dSTRIDE), in nuclei of single cells, using fluorescence microscopy. Sensitivity of STRIDE was tested using specially developed CRISPR/Cas9 DNA damage induction system, capable of inducing small clusters or individual single- or double-strand breaks. STRIDE exhibits significantly higher sensitivity and specificity of detection of DNA breaks than the commonly used TUNEL assay or methods based on monitoring of recruitment of repair proteins or histone modifications at the damage site (e.g. {gamma}H2AX). Even individual genome site-specific DNA double-strand cuts induced by CRISPR/Cas9, as well as individual single-strand DNA scissions induced by the nickase version of Cas9, can be detected by STRIDE and precisely localized within the cell nucleus. We further show that STRIDE can detect low-level spontaneous DNA damage, including age-related DNA lesions, DNA breaks induced by several agents (bleomycin, doxorubicin, topotecan, hydrogen peroxide, UV, photosensitized reactions), and fragmentation of DNA in human spermatozoa. STRIDE methods are potentially useful in studies of mechanisms of DNA damage induction and repair in cell lines and primary cultures, including cells with impaired repair mechanisms.

cell biology↗

bioRxiv2017

CRISPR-Based DNA Imaging in Living Cells Reveals Cell Cycle-Dependent Chromosome Dynamics

In contrast to the well-studied condensation and folding of chromosomes during mitosis, their dynamics in interphase are less understood. We developed a sensitive, multicolor system, CRISPR-Sirius, allowing the real-time tracking of the dynamics of chromosomal loci. We tracked loci kilobases to megabases apart and found significant variation in the inter-locus distances of each pair, indicating differing degrees of DNA contortion. We resolved two distinct modes of dynamics of loci: saltatory local movements as well as translational movements of the domain. The magnitude of both of these modes of movements increased from early to late G1, whereas the translational movements were reduced in early S. The local fluctuations decreased slightly in early S and more markedly in mid-late S. These newly observed movements and their cell cycle-dependence are indicative of a hitherto unrecognized compaction-relaxation dynamic of the chromosomal fiber operating concurrently with changes in the extent of observed genomic domain movements.\n\nIN BRIEFDistinct chromosome folding and dynamics during cell cycle progression were dissected by CRISPR-Sirius DNA imaging in living cells.\n\nHIGHLIGHTSO_LICRISPR-Sirius allows tracking of pairs of chromosomal loci having kilobase to megabase inter-locus distances\nC_LIO_LIPair-wise tracking of loci allows measurement of both local and domain dynamics\nC_LIO_LIChromosomal fiber relaxation is positively correlated with local dynamics\nC_LIO_LIGenomic region size contributes to local and domain movements\nC_LIO_LIDistinct chromosome dynamics were uncovered during cell cycle progression in interphase\nC_LI

cell biology↗